Unit5

• catalyst- a substance that increases the rate of a chemical reaction and is not changed by it
• enzymes- proteins that function as biological catalyst
• sum of all chemical reactions that occurs in a living organism is called metabolism
• catabolic reaction- chemical reactions in which large molecules are broken down from smaller molecules
• anabolic reaction- chemical reaction in which smaller molecules are combined to form larger molecules
• enzymes either:

  • break large molecules into smaller ones
  • build large molecules from smaller ones
  • convert one small molecule to another
• an enzyme is a biological catalyst:

  • they speed up the reaction
  • they are proteins
  • they are reusable
  • can be denatured
  • influenced by temperature and PH
• proteins:

  • pepsin into peptides
  • trypsin into amino acid
• starch- amylase into maltose
• maltose into glucose by maltase
• fat/oil/lipids- lipase into fatty acids and glycerol
• substrate/reactant- substances that undergo chemical reaction
• products- substances which are formed as a result of a chemical reaction
• enzyme action:

  • the molecules on which enzyme act is called a substrate
  • the substrate binds with active-site of the enzyme
  • active-site is the part of the enzyme molecule on which substrate binds
  • then the enzyme converts the substrate into products
• lock and key hypothesis(enzyme action)- because enzyme has a specific site like the lock, where substrate molecules can fi. this is the same as specific key fitting into a lock.
• optimum temperature of enzyme- the temperature at which enzyme works at best
• below optimum(enzyme)- rate of reaction is slow, at low temperature enzyme and substrate has less kinetic energy and moves slowly
• when the temperature increases up to optimum- enzyme and substrate gain more kinetic energy and moves faster, increasing the rate of the reaction
• at optimum temperature - rate of the reaction will be the fastest
• above optimum temperature- the rate of the reaction slows down as enzymes get denatured
• optimum temperature for human enzymes is 37 -40* C - lower than this, enzymes are inactivated. Higher than this enzymes start to denature
• Enzymes are folded into a shape that accepts the substrate molecule. This is determined by the sequence of amino acids that form it. As you approach the optimum temp, enzymes gain kinetic energy, and so collisions with substrates are more frequent. As a result, the rate of reaction is highest. As you go beyond the optimum temp, bonds holding enzymes break down, the shape of the active site changes. So it is ​denatured
• enzymes are affected by acidity or alkalinity (PH) of the meduim they work in
• if the PH falls on either side of optimum PH, enzyme activity gradually decreases. because extreme PH destroys the shape of the enzyme, hence changing the shape of the active-site
• PH levels in :

  • pepsin- proteins in stomach so pH2
  • amylase- starch in mouth so pH 7
  • trypsin- proteins in small intestine so 8